The number 6 has a special significance. It represents the Law and Order and also associated with a Karmic Law of cause and effect. Number 6 is a perfect number, symmetrical in all parts, the number of the Soul.
Plums are ready they are not hard as a rock, soft just a little when pressed. I wouldn't use windfall, they are too ripe. If your making jam, it is best to use some underripe with the ripe ones. Last season I added small diced candied ginger to the plum jam. Really turned out nice.
Storing Ripe Plums. Once plums have ripened, either on the tree or off, they keep well in the crisper section of the refrigerator. Store ripe plums in an open plastic bag for two to four weeks. Bring them back to room temperature just before eating for best fresh flavor. University of Illinois Extension: Plums.